International classification of noise-optimized surfaces compared to SDA
International is only a part of the noise-reducing pavements that follow a similar concept to the Swiss SDA that are actually classified as "semi-dense." The requirements in international standards partially overlap with those of the Swiss SDA pavement. The central commonalities lie particularly in the void content (VC) of 10–18 % and the layer thickness (LT) of 30 ± 10 mm.
As the following table shows, formulations with comparable properties to SDA are referred to by very different terms in various countries – such as "thin-layer," "porous," "dense," or under variants of SMA (Stone Mastic Asphalt). In South Africa, for example, there is a "gap-graded" formulation that has a void content of only 3–6 %.
These differences highlight the need for international standardization of names and classifications – for both SDA and PA (Porous Asphalt).
List of SDA pavements available outside Switzerland (Saurer, Bühlmann and Ziegler, 2016)1
|
Country |
Designation |
Void Content (VC) |
Max. Grain Size |
Layer Thickness |
Special Features |
|
Denmark |
Thin noise-reducing pavement |
12–16% |
6–8 mm |
n/a |
Relatively thin, noise-reducing |
|
Germany |
SMA LA 5/8 |
9–14% |
5/8 mm |
n/a |
Predecessor of the Swiss SDA |
|
Austria (LSMA) |
LSMA 8 or 11 mm |
n/a |
8 or 11 mm |
n/a |
semi-dense, noise-reducing |
|
Austria (BBTM) |
BBTM 5 or 8 mm |
11–15% |
5 or 8 mm |
n/a |
Thin-layer, similar properties to SDA |
|
India |
SDA Standard |
5–10% |
up to 20 mm |
n/a |
National standard since 1987 |
|
New Zealand |
PA HS (TNZ P/11:2007) |
12–16% |
n/a |
n/a |
Suitable for high shear loads |
|
Netherlands |
Various semi-dense mixtures |
8–10% to 15–19% |
5.6–8 mm |
n/a |
Wide range of semi-dense mixtures |
|
Sweden (DAC 8) |
DAC 8 |
10–12% |
8 mm |
35 mm |
semi-dense, noise-reducing |
|
Sweden (ABD 11) |
ABD 11 |
n/a |
11 mm |
n/a |
Porous structure |
|
Spain |
SDA category |
6–12% |
12–20 mm |
n/a |
Own SDA definition in Spain |
|
USA (OGAC) |
OGAC |
approx. 15% |
n/a |
25–30 mm |
Varies by state |
Learn more about LAB in the international context
Denmark has introduced a number of relatively thin noise-reducing pavements, some of which have a void content (VC) of 12–16 % and a maximum grain size of 6–8 mm (Sandberg et al., 2011).2
In Germany, the stone mastic asphalt “SMA LA 5/8” is used with a VC of 9–14 %. This pavement is considered the main predecessor of today's SDA pavements in Switzerland.
In Austria, there are two variants of semi-dense noise-reducing pavements:
-
Noise-reducing SMA 8 (LSMA 8 or 11 mm)
-
Noise-reducing thin-layer pavements (BBTM 5 or 8 mm)
The BBTM has a porosity of 11–15 % and smaller aggregate sizes. This makes it similar to the Swiss SDA mixtures, but it is constructed thinner (Wehr, Reinhard et al., 2020)3 .
In India, there has been a standard for SDA pavements since 1987. This specifies a maximum grain size of 20 mm, a VC of 5–10 %, and a binder content of 4.5–6 %. The layer thickness varies between 25 and 40 mm depending on the grain size (Indian Roads Congress, 1987)4 .
New Zealand defines in the standard TNZ P/11:2007 a special PA mixture called PA HS (High Shear). It is intended for applications where conventional PA mixtures with higher void content tend to shear stresses. The required void content is in the range of 12–16 %, comparable to SDA (Transport New Zealand, 2007).5
The Netherlands are pioneers in the use of porous pavements. Numerous semi-dense formulations have been developed – with grain sizes of 5.6–8 mm and VC values between 8–10 % and 15–19 %. Nevertheless, primarily noise-reducing PA pavements are used there. In Austria, a “SMA 8” mixture is used that resembles the types used in the Netherlands and Germany.
In Sweden, the combination of porosity and rubber has often been used for noise reduction, for example in the PoroElastic Road Surface (PERS). These pavements offer excellent acoustic properties (Sandberg et al., 2013), but are not sufficiently resistant to conditions with Swedish winter tires. In addition, pavements resembling SDA have also been used, such as the semi-dense DAC 8 with a VC of 10–12 % and an LT of 35 mm (Saurer, Bühlmann and Ziegler, 2016)6 . A more porous variant is the ABD 11 (Ongel, Harvey and Kohler, 2007).7
In Spain, the responsible road construction authorities have introduced their own SDA category for noise-reducing asphalt pavements. This defines a void content of 6–12 % and a maximum grain size between 12 and 20 mm (Pérez Pérez et al., 2010; Bueno et al., 2011).8
In the USA, so-called Open Graded Asphalt Concrete (OGAC) is used in several states. The properties of these pavements vary depending on the climatic and infrastructural conditions of the respective states. Some OGAC mixtures fall within the SDA range with a VC of about 15 % and an LT of 25–30 mm (Ongel, Harvey and Kohler, 2007)9 . Compared to Switzerland, the USA is more federally organized in this regard, as regional differences in climate must be taken into greater account.